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Understanding the problem domain is the hardest part of programming

Writing code is a lot like putting together a jigsaw puzzle. We put together code with the purpose of building components that we have taken out of the “bigger picture” of the problem domain.

The big issue is that many problem domains are like a puzzle with a blurry picture or no picture at all.

As programmers, we also are often not given complete information about the problem domain, so we don’t even have the information we need to understand it.

Programming is easy if you understand the problem domain

  • Make the problem domain easier

You can often make the problem domain easier by cutting out cases and narrowing your focus to a particular part of the problem.

What I mean by this is that it is often beneficial to take a part of the problem and fully understand that part before expanding the problem domain.

  • Get better at understanding the problem domain

make sure you understand a problem inside and out before you try and solve it with code.

Chapter 3: “Object Literals” (pp.100-105)

function declaration creates a function that you can call later in your code. It is the type of function you have seen so far in this book. In order to call the function later in your code, you must give it a name, so these are known as named functions B

If you put a function where the interpreter would expect to see an expression, then it is treated as an expression, and it is known as a function expression.

In function expressions, the name is usually omitted. A function with no name is called an anonymous function.

When a variable is created inside a function using the var keyword, it can only be used in that function. It is called a local variable or function-level variable. It is said to have local scope or function-level scope. It cannot be accessed outside of the function in which it was declared.

If you create a variable outside of a function, then it can be used anywhere within the script. It is called a global variable and has global scope.

Chapter 5: “Document Object Model” (pp.183-242)

The key difference between a whi 1 e loop and a do whi 1 e loop is that the statements in the code block come before the condition. This means that those statements are run once whether or not the condition is met.

ACCESS THE ELEMENTS

Here is an overview of the methods and properties that access elements

  • Here are three common ways to

  • select an individual element:

Uses the value of an element's id attribute (which should be unique within the page).

  • Uses a CSS selector, and returns the first matching element.

  • You can also select individual elements by traversing from one element to another within the DOM tree (see third column).

  • There are three common ways to select multiple elements.

  • getElementsByClassName() Selects all elements that have a specific value for their cl ass attribute.

  • getElementsByTagName() Selects all elements that have the specified tag name ..

  • querySelectorAll() Uses a CSS selector to select all matching elements.

get El ementByi d () allows you to select a single element node by specifying the value of its id attribute.

This method has one parameter: the value of the id attribute on the element you want to select. This value is placed inside quote marks because it is a string. The quotes can be single or double quotes, but they must match.

The code then uses a property called cl assName to update the value of the cl ass attribute of the element stored in this variable. Its value is coo 1, and this triggers a new rule in the CSS that sets the background color of the element to aqua. Note how the c 1 assName property is used on the variable that stores the reference to the element.

  • This property finds the element node for the containing (or parent) element in the HTML. (1) If you started with the first element, then its parent node would be the one representing the

      element.

    • These properties find the previous or next sibling of a node if there are siblings. If you started with the first <1 i > element, it would not have a previous sibling. However, its next sibling (2) would be the node representing the second .

    • lastChild These properties find the first or last child of the current element. If you started with the <u 1 > element, the first child would be the node representing the first element, and (3) the last child would be the last <1 i >.

    STORE THE ELEMENT

    TO BE REMOVED IN A VARIABLE You start by selecting the element that is going to be removed and store that element node in a variable.

    When you remove an element from the DOM, it will also remove any child elements.

    STORE THE PARENT OF THAT ELEMENT IN A VARIABLE

    you find the parent element that contains the element you want to remove and store that element node in a variable. The simplest way to get this element is to use the parentNode property of this element.

    REMOVE THE ELEMENT FROM ITS CONTA INING ELEMENT

    The removeChi ld() method is used on the containing element that you selected in step 2. The removeChi ld() method takes one parameter: the reference to the element that you no longer want.